Angiogenesis, the growth of capillary blood vessels is necessary for tumor growth, tumor progression, and metastasis. Antiangiogenic therapy has been successfully demonstrated in animals and an angiogenesis inhibitor discovered by us in the previous grant period is now being prepared for clinical trial. Angiogenesis is also fundamental to reproduction, development and repair. Under these conditions, angiogenesis is highly regulated. In neoplasia and in certain other non-neoplastic diseases this regulation is perturbed, resulting in persistent, unabated angiogenesis. In this Program Project, a closely knit group of investigators will study the regulation of angiogenesis at the molecular, biochemical and cellular levels. A novel heparin-binding inhibitor of endothelial cell proliferation produced by macrophages and monocytes will be purified and cloned. Another natural endothelial inhibitor recently purified from cartilage will be studied to determine how its down-regulation may operate during the onset of tumor angiogenesis. The mechanism by which physical forces are transmitted across extracellular matrix receptors (integrins) and transduced into changes of nuclear structure and function will be analyzed to discover how extracellular matrix regulates capillary endothelial cell sensitivity to soluble mitogens. The mechanisms of vascular morphogenesis will be investigated by analyzing normal and transformed endothelial cells for their effects on mural cell growth and function and by determining if there is a role for exogenous stretch in vascular growth control. A new endothelial cell surface lectin which by interaction with specific carbohydrates proves instructions for lumen formation during angiogenesis, will be characterized. The role of mast cells in angiogenesis will be studied by purifying a novel tumor-derived chemoattractant for mast cells and by investigating the mechanism by which alpha-interferon causes involution of mast cell-rich hemangiomas (Zetter). In preparation for clinical trial of antiangiogenic therapy, methods for detecting angiogenic activity in human serum and urine will be developed, a quantitative angiogenesis inhibitor bioassay will be perfected, and a study of circulating endothelial cell inhibitors will be initiated. All of these studies in this Program Project Grant are focused on a general theme of identifying potential new targets for angiogenesis inhibition, new inhibitory molecules, or new biology of the angiogenic process so that antiangiogenic therapy in cancer may be successfully applied in future clinical trials.